RFR: Remove ShFastSyncRoots

[Roman Kennke]

> On 09/26/2018 08:07 PM, Roman Kennke wrote:
>> We have a fast synchronizer roots iterator, but it's not really used. It
>> used to be useful when we did not have thread-local MonitorInUseLists
>> and needed to scan one global list efficiently, but MonitorInUseLists
>> provides much more natural parallelization via thread stacks. Also,
>> MonitorInUseLists is deprecated and I see no point why anybody would
>> disable it. Let's remove the extra cruft:
>>
>> http://cr.openjdk.java.net/~rkennke/remove-fast-syncroots/webrev.00/
> 
> *) I don't understand the removal of upstream code in src/hotspot/share/runtime/synchronizer.cpp:
> ObjectSynchronizer::verifyInUse, block in ::InduceScavenge, etc. We only have
> ParallelObjectSynchronizerIterator added:
> 
> https://builds.shipilev.net/patch-openjdk-shenandoah-jdk/v99-vs-15094d12a632/src/hotspot/share/runtime/synchronizer.cpp.sdiff.html

Oops. I've copied over from jdk/jdk but from tip not from jdk-12+12 as I
should have:

http://cr.openjdk.java.net/~rkennke/remove-fast-syncroots/webrev.01/

Good?